1. Field of the Invention
This invention relates to ferrules having an optical fiber incorporated therein as an integral part thereof (hereinafter referred to occasionally as xe2x80x9cferrule of the optical fiber built-in typexe2x80x9d) for connecting and/or fixing optical fiber ends or optical fiber cable ends to be used in optical communications. This invention also relates to methods for the production thereof.
2. Description of the Prior Art
Parts for optical connectors are required to have high dimensional accuracy in order to prevent the loss of light. More specifically, for the sake of coincidence between the axes of the optical fibers and the prevention of the loss of light, the parts for fixing and aligning the optical fibers require the machining with high accuracy in the order of submicrons.
The conventional method for the production of an optical connector ferrule (hereinafter referred to occasionally as xe2x80x9ccapillaryxe2x80x9d) comprises the steps of first molding a suitable material such as a ceramic powder containing a binder, a synthetic resin, and a metal by injection molding, extrusion molding or the like thereby forming a ferrule blank (Japanese Patent Publication No. 8-30775B, Japanese Patent Applications, KOKAI (Early Publication) No. (hereinafter referred to briefly as xe2x80x9cJP-A-xe2x80x9d) 8-15568, JP-A-8-194131, JP-A-9-141704, JP-A-10-186176, etc.), degreasing and sintering the resultant blank depending on the material used, and finishing the blank into a desired dimension by subjecting it to machining such as abrasive finishing of the outside diameter, abrasive finishing of the inside diameter, and polishing of the leading end into the spherical convex surface (PC polishing). Since the inside diameter of a small hole of the ferrule for the insertion of an optical fiber is very small (for instance, the diameter of the small hole of the capillary of the SC type is 0.126 mm), the wire lapping finishing is commonly used for the finishing of the inside diameter thereof. Accordingly, the process of production is lengthy and requires expensive apparatuses such as an inside diameter finishing machine and an outside diameter finishing machine, and the cost of production is inevitably large.
When the optical connector ferrule (capillary) is produced by the conventional injection molding, the formation of the small hole for the insertion of an optical fiber will inevitably require the use of a core pin having a minute diameter of about 0.1 mm. This process, therefore, has the problem of exposing the core pin to the possibility of sustaining breakage or bending during the casting or during the operation of drawing of the core pin after casting. Further, since the core pin is expensive, the breakage or the bending of the core pin forms a large factor for boosting the cost of the ferrule.
Moreover, the small hole for the insertion of an optical fiber formed as described above must be subjected to the inside diameter finishing in order to smoothen the inside surface of the hole and to acquire high circularity or roundness in cross section and sufficient dimensional accuracy thereof. The process of production, therefore, incurs an enormous cost inevitably.
When an optical fiber is inserted and fixed into the small hole of the ferrule formed as described above, it is necessary to apply an adhesive to the leading end of the optical fiber and then insert it into the small hole. Since the adhesive used in this operation is hygroscopic and thus deteriorates with time, it will be difficult to stably use the ferrule having the optical fiber fixed therein for a long time. Further, since the coefficient of linear thermal expansion of the optical fiber greatly differs from that of the adhesive (for instance, the coefficient of linear thermal expansion of quartz fiber is 0.5xc3x9710xe2x88x926/K, those of the ferrule materials are, for example, 10xc3x9710xe2x88x926/K in a metallic glass and 9xc3x9710xe2x88x926/K in zirconia, while that of the adhesive is 30-40xc3x9710xe2x88x926/K), the product will bring about such problem as separation of the optical fiber from the ferrule due to the heat cycle in the use.
The small hole of the ferrule for the insertion of an optical fiber is so designed as to have an inside diameter slightly greater than the outside diameter of the optical fiber to secure the insertion of the optical fiber into the small hole of the optical connector ferrule. This dimensional design, however, incurs the problem that, when the optical fiber is inserted and fixed into the small insertion hole, the center of the optical fiber 10 deviates from the center of the ferrule 12 as shown in FIG. 1 in the deformed form. Such axial deviation greatly affects the connector insertion loss of the optical fibers.
It is, therefore, an object of the present invention to provide an inexpensive ferrule having an optical fiber strongly incorporated therein as an integral part thereof with high positional accuracy, which will not incur the problems caused by the use of a core pin or an adhesive as mentioned above and the problem that an optical fiber separates from the ferrule due to the deterioration of an adhesive caused by the heat cycle in the use.
A further object of the present invention is to provide a method which allows a ferrule of the optical fiber built-in type satisfying a predetermined shape, dimensional accuracy, and surface quality to be mass-produced with high efficiency by a simple process without requiring the use of a core pin and, therefore, enables to omit such machining steps as inside diameter finishing of the ferrule and adhesion of an optical fiber to the ferrule, thereby lowering the cost of production of the ferrule.
To accomplish the object mentioned above, the first aspect of the present invention provides a ferrule having an optical fiber incorporated therein as an integral part thereof.
The first embodiment of the ferrule according to the present invention is characterized by having an optical fiber integrally fixed therein during the production of an optical connector ferrule.
The second embodiment of the ferrule is characterized by comprising an optical connector ferrule, a metal tube embedded therein in the longitudinal direction thereof, and an optical fiber fitted into the metal tube, wherein the optical fiber is integrally fixed in the ferrule through the medium of the metal tube during the production of the ferrule.
In either embodiment mentioned above, preferably the optical fiber or both the optical fiber and the metal tube are strongly fixed in the ferrule by the thermal shrinkage or coagulation shrinkage of the optical connector ferrule during the production thereof.
The optical fiber may be in the form of extending only in the interior of the optical connector ferrule from one end to the other end thereof or further continuously extending outward from one end of the optical connector ferrule.
In one concrete embodiment, the metal tube has an inside diameter ranging from 0.1 mm to 1.0 mm and an outside diameter ranging from 0.14 mm to 2.3 mm and the ferrule has an outside diameter ranging from 0.2 mm to 2.5 mm.
The ferrule mentioned above may be manufactured from a metal, an amorphous alloy containing an amorphous phase in a volumetric ratio of at least 50%, ceramics or a synthetic resin.
In a preferred embodiment, the ferrule having an optical fiber incorporated therein as an integral part thereof is characterized by being formed of a substantially amorphous alloy having a composition represented by either one of the following general formulas (1) to (6) and containing an amorphous phase in a volumetric ratio of at least 50%:
M1aM2bLncM3dM4eM5fxe2x80x83xe2x80x83(1)
wherein M1 represents either or both of the two elements, Zr and Hf; M2 represents at least one element selected from the group consisting of Ni, Cu, Fe, Co, Mn, Nb, Ti, V, Cr, Zn, Al, and Ga; Ln represents at least one element selected from the group consisting of Y, La, Ce, Nd, Sm, Gd, Tb, Dy, Ho, Yb, and Mm (mish metal: aggregate of rare earth elements); M3 represents at least one element selected from the group consisting of Be, B, C, N, and O; M4 represents at least one element selected from the group consisting of Ta, W, and Mo; M5 represents at least one element selected from the group consisting of Au, Pt, Pd, and Ag; and a, b, c, d, e, and f represent such atomic percentages as respectively satisfy 25xe2x89xa6axe2x89xa685, 15xe2x89xa6bxe2x89xa675, 0xe2x89xa6cxe2x89xa630, 0xe2x89xa6dxe2x89xa630, 0xe2x89xa6exe2x89xa615, and 0xe2x89xa6fxe2x89xa615.
Al100xe2x88x92gxe2x88x92hxe2x88x92iLngM6hM3ixe2x80x83xe2x80x83(2)
wherein Ln represents at least one element selected from the group consisting of Y, La, Ce, Nd, Sm, Gd, Tb, Dy, Ho, Yb, and Mm; M6 represents at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Hf, Ta, and W; M3 represents at least one element selected from the group consisting of Be, B, C, N, and O; and g, h, and i represent such atomic percentages as respectively satisfy 30xe2x89xa6gxe2x89xa690, 0xe2x89xa6hxe2x89xa655, and 0xe2x89xa6ixe2x89xa610.
Mg100xe2x88x92pM7pxe2x80x83xe2x80x83(3)
wherein M7 represents at least one element selected from the group consisting of Cu, Ni, Sn, and Zn; and p represents an atomic percentage falling in the range of 5xe2x89xa6pxe2x89xa660.
Mg100xe2x88x92qxe2x88x92rM7qM8rxe2x80x83xe2x80x83(4)
wherein M7 represents at least one element selected from the group consisting of Cu, Ni, Sn, and Zn; M8 represents at least one element selected from the group consisting of Al, Si, and Ca; and q and r represent such atomic percentages as respectively satisfy 1xe2x89xa6qxe2x89xa635 and 1xe2x89xa6rxe2x89xa625.
Mg100xe2x88x92qxe2x88x92sM7qM9sxe2x80x83xe2x80x83(5)
wherein M7 represents at least one element selected from the group consisting of Cu, Ni, Sn, and Zn; M9 represents at least one element selected from the group consisting of Y, La, Ce, Nd, Sm, and Mm; and q and s represent such atomic percentages as respectively satisfy 1xe2x89xa6qxe2x89xa635 and 3xe2x89xa6sxe2x89xa625.
Mg100xe2x88x92qxe2x88x92rxe2x88x92sM7qM8rM9sxe2x80x83xe2x80x83(6)
wherein M7 represents at least one element selected from the group consisting of Cu, Ni, Sn, and Zn; M8 represents at least one element selected from the group consisting of Al, Si, and Ca; M9 represents at least one element selected from the group consisting of Y, La, Ce, Nd, Sm, and Mm; and q, r, and s represent such atomic percentages as respectively satisfy 1xe2x89xa6qxe2x89xa635, 1xe2x89xa6rxe2x89xa625, and 3xe2x89xa6sxe2x89xa625.
The second aspect of the present invention provides methods for the production of the ferrules having an optical fiber incorporated therein as an integral part thereof as mentioned above.
One mode of the methods is characterized by comprising the steps of inserting an optical fiber into a mold provided with a molding cavity which defines the outer shape of an optical connector ferrule so as to be disposed in the cavity, injecting a fluid material kept at an elevated temperature into the cavity of the mold, and solidifying the injected material by cooling, thereby strongly fixing the optical fiber in the ferrule produced.
Another mode of the methods is characterized by comprising the steps of inserting a metal tube having an optical fiber fitted therein into a mold provided with a molding cavity which defines the outer shape of an optical connector ferrule so as to be disposed in the cavity, injecting a fluid material kept at an elevated temperature into the cavity of the mold, and solidifying the injected material by cooling, thereby strongly fixing the optical fiber in the produced ferrule through the medium of the metal tube embedded in the ferrule.
In a preferred embodiment of this method, the optical fiber is set in the mold so as to have at least one end thereof continuously extended outward from the mold and the ferrule is produced while applying a tension load to the optical fiber during the production.
As a material for the ferrule mentioned above, a metal, an amorphous alloy containing an amorphous phase in a volumetric ratio of at least 50%, a ceramic paste, a synthetic resin or the like may be used.
In another preferred embodiment, the material mentioned above is a melt of an alloying material capable of producing a substantially amorphous alloy having a composition represented by either one of the aforementioned general formulas (1) to (6) and containing an amorphous phase in a volumetric ratio of at least 50%, and this molten alloy is forcibly transferred into the cavity of the mold mentioned above and rapidly solidified in the mold to confer amorphousness on the alloy.